Candela Laser Corporation proposes to develop a new glaucoma surgery in which laser energy is used to remove trabecular tissue atraumatically. Both Nd:YAG laser trabeculopuncture and conventional trabeculotomy have been used to treat open-angle glaucoma, but these techniques cause mechanical damage to the trabecular meshwork, leading to scarring and failure of the procedure. If trabecular tissue could be ablated with minimal mechanical or thermal damage, the reduction in wound healing response may result in improved long term success. Erbium YAG laser radiation (wavelength 2.94 um) is very strongly absorbed by tissues (absorption length 1 um); therefore, ablation with the Er:YAG laser causes minimal collateral tissue damage. The optimum laser parameters for trabecular ablation will be determined by a histological study following Er:YAG ablation of eye bank tissue. Trabecular ablation in cynomolgus monkeys will be performed using the optimized pulse duration and energy. Intraocular pressure and aqueous outflow facility will be monitored for 3 months postoperatively. Trabecular surgery is a potentially attractive alternative to filtration surgery because of theoretically lower incidences of post-operative hypotony, flat anterior chambers, scarring in the subconjunctival space, and late endophthalmitis from infected blebs.